zh-CN: create extension.getBackgroundPage()

files/zh-cn/mozilla/add-ons/webextensions/api/extension/getbackgroundpage/index.md

@@ -0,0 +1,89 @@
+---
+title: extension.getBackgroundPage()
+slug: Mozilla/Add-ons/WebExtensions/API/extension/getBackgroundPage
+l10n:
+  sourceCommit: d82c19fea93f7b36787c6d84af600c955c2732d5
+---
+
+{{AddonSidebar}}
+
+若后台脚本在运行中，则返回后台页面的 [Window](/zh-CN/docs/Web/API/Window)。若脚本不在运行，则返回 null。
+
+这是一个同步函数。
+
+> [!NOTE]
+> 该方法不能在隐私浏览模式下使用——它总是返回 null。请考虑使用 {{WebExtAPIRef("runtime.sendMessage","runtime.sendMessage()")}} 或 {{WebExtAPIRef("runtime.connect","runtime.connect()")}}。更多信息请参见 [Firefox bug 1329304](https://bugzil.la/1329304)。
+
+## 语法
+
+```js-nolint
+let page = browser.extension.getBackgroundPage()
+```
+
+### 参数
+
+无。
+
+### 返回值
+
+`object`。后台页面的 [Window](/zh-CN/docs/Web/API/Window) 或 null。
+
+## 示例
+
+考虑定义了一个 `foo()` 函数的[后台脚本](/zh-CN/docs/Mozilla/Add-ons/WebExtensions/Anatomy_of_a_WebExtension#后台脚本)：
+
+```js
+// background.js
+
+function foo() {
+  console.log("我是在 backgroubd.js 中被定义的");
+}
+```
+
+在[弹窗](/zh-CN/docs/Mozilla/Add-ons/WebExtensions/user_interface/Popups)中运行的脚本可以直接调用这个函数：
+
+```js
+// popup.js
+
+let page = browser.extension.getBackgroundPage();
+page.foo(); // -> "我是在 background.js 中被定义的"
+```
+
+{{WebExtExamples}}
+
+## 浏览器兼容性
+
+{{Compat}}
+
+> [!NOTE]
+> 此 API 基于 Chromium 的 [`chrome.extension`](https://developer.chrome.google.cn/docs/extensions/reference/api/extension/#method-getBackgroundPage) API。该文档衍生自 Chromium 代码中的 [`extension.json`](https://chromium.googlesource.com/chromium/src/+/master/chrome/common/extensions/api/extension.json)。
+
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